What is LL-37 sold for here?

This product is sold exclusively as a laboratory chemical for research, not as a pharmaceutical, and is not intended for human or animal use. LL-37 does not hold market authorization as a drug.

What exactly is LL-37?

LL-37 is the only human cathelicidin, a 37-amino-acid, cationic antimicrobial peptide. It is cleaved by Proteinase 3 from the precursor protein hCAP18, which is encoded by the CAMP gene. The molecular mass is approximately 4493 Da (free acid form).

How are the identity and purity of LL-37 confirmed?

Identity is verified by mass spectrometry, together with an HPLC purity result on the batch certificate. The report is issued by Janoshik and submitted by the manufacturer; current batch values are listed on our CoA page.

What did the Grönberg study on venous leg ulcers show?

Grönberg et al. (Wound Repair Regen 2014, PMID 25041740) conducted a randomized first-in-human trial in 34 patients with hard-to-heal venous leg ulcers. The lowest topical dose (0,5 mg/ml) achieved an approximately six-fold higher healing rate constant than placebo; the dose-response was non-monotonic, and the highest dose (3,2 mg/ml) showed no benefit.

What did the study on diabetic foot ulcers show?

A randomized, double-blind, placebo-controlled trial (Arch Dermatol Res 2023, PMID 37480520) examined an LL-37 cream in diabetic foot ulcers with mild infection and reported accelerated wound healing with improved granulation. Inflammatory markers (IL-1α, TNF-α) and aerobic bacterial colonization did not decrease significantly, meaning the healing effect did not run through a measurable reduction in these markers.

What did the Zhao COVID study show?

Zhao et al. (J Med Virol 2023) conducted a randomized, placebo-controlled, open-label trial in 238 hospitalized patients. The intervention was an oral, LL-37-expressing recombinant Lactococcus lactis (a genetically engineered probiotic), not the synthetic LL-37 peptide sold here. With early treatment onset, the time to viral load negativity was shortened (approximately 9,8 versus 14,0 days). The proposed mechanisms are hypotheses; the open-label design and the formulation limit transferability to the synthetic peptide.

LL-37 acts through at least two modes: at higher concentrations, the cationic amphipathic helix permeabilizes bacterial membranes; at sub-lethal concentrations, it acts as an immunomodulator (e.g., recruitment of neutrophils, influencing dendritic cells, and, in preclinical models, activation of the STING signaling pathway). The immunomodulatory details are derived predominantly from cell and animal models.

Is LL-37 active against resistant bacteria?

In vitro, LL-37 is active against MRSA, VRE, and representatives of the ESKAPE panel, which is why it serves as a reference molecule in the development of antimicrobial peptides (see review e.g. Keshri et al., Int J Antimicrob Agents 2025, PMID 39643165). This is in-vitro and preclinical research, not an approved therapy.

What role does Vitamin D play with LL-37?

Transcription of the CAMP gene is strongly induced by Vitamin D via a Vitamin D response element. This is why serum 25(OH)D status can be considered a relevant covariate in cathelicidin studies; this is relevant for interpreting the evidence.

Are there any safety concerns with LL-37?

LL-37 has a context-dependent dual role in cancer biology: it is pro-angiogenic and, depending on the model, can be either tumor-promoting or tumor-suppressive (see review Zhang et al.). Extrapolating from wound-healing or antimicrobial contexts to other settings is therefore not straightforward. No dedicated safety data exist for the research-grade material sold here.

What dosages have been used in research?

In the controlled wound-healing trial (Grönberg 2014), topical LL-37 concentrations of 0,5 to 3,2 mg/ml were used, with the strongest effect at the lowest dose. Non-validated community reports cite differing orders of magnitude; these figures are self-reported and not a recommendation. There is no EU-approved treatment regimen for human use.

LL-37 is more labile than small peptides. The lyophilized powder is stored at -20 °C, ideally at -80 °C for long-term archiving. After reconstitution, LL-37 is light-sensitive; store refrigerated (2-8 °C) and protected from light, and avoid repeated freeze-thaw cycles. A fixed shelf life cannot be guaranteed without a batch-specific stability study.

What is LL-37 reconstituted with?

In laboratory practice, bacteriostatic water (0,9% benzyl alcohol) is often used. Let the liquid run slowly down the vial wall and swirl gently, without shaking. This does not establish validated compatibility or stability with LL-37; the protocol should specify a suitable, validated solvent.

Is LL-37 an approved medication?

No. LL-37 does not hold market authorization as a drug and has not been approved as a medication in any region. The existing human trials are early, in some cases small, controlled studies; it is sold here exclusively as a research chemical.

Is it legal to buy LL-37 for research in the EU?

There is no uniform EU-wide category for research peptides; the legal situation depends on presentation, intended use, and the national law of the respective member state. We sell exclusively for laboratory research, not for human consumption. Please clarify the rules with your national competent authority and your institution, seek qualified legal advice if needed, and treat this as general information, not legal advice.

Buy LL-37: What Researchers Should Know About the Human Cathelicidin Peptide

LL-37 occupies an unusual position among research peptides. Its sequence corresponds to a naturally occurring human molecule that is released from the hCAP18 precursor and found in neutrophils, epithelia, and mucosal surfaces; the peptide sold here is manufactured synthetically. What makes LL-37 particularly interesting for researchers in 2026: unlike many peptides discussed on this blog, it has been studied in controlled human trials (Grönberg 2014, a 2023 RCT on diabetic foot ulcers, and the 2023 COVID-19 study by Zhao, which however used an LL-37-expressing probiotic rather than the synthetic peptide). That sets it clearly apart from the predominantly preclinical data available for most peptides of this size.

LL-37regeneration

Cathelicidin-derived antimicrobial peptide (37 amino acids). Researched for innate immunity, antimicrobial activity, and wound-healing pathways. ≥98% HPLC purity with Janoshik CoA.

Background: Origin and Sequence

LL-37 is the only human cathelicidin, a 37-amino-acid peptide that begins with two leucines (hence the name "LL"). It is cleaved by Proteinase 3 from the 18 kDa cationic antimicrobial protein hCAP18, which is encoded by the CAMP gene on chromosome 3. The mature sequence is:

LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES

This amphipathic alpha-helix is strongly cationic at physiological pH, which explains both its membrane activity and its secondary immunomodulatory functions. Unlike BPC-157 or Thymosin Beta-4, LL-37 exists natively in the human body and is expressed in neutrophil granules and macrophages; in keratinocytes, baseline expression is low and is induced by injury or inflammation. Its expression is strongly induced by Vitamin D via the VDR response element in the CAMP promoter, a relationship known since the mid-2000s that remains clinically relevant for interpreting LL-37 studies.

Why Is LL-37 Studied So Intensively?

Three research lines dominate the LL-37 literature: wound healing, antimicrobial resistance (AMR), and, more recently, viral inhibition including SARS-CoV-2.

On wound healing, Heilborn and colleagues showed in 2003 (J Invest Dermatol, PMID 12603850) that LL-37 is required for re-epithelialization of human skin wounds. Reduced LL-37 expression has been documented in chronic venous ulcers, providing a biological rationale for substitution. This line of research includes a randomized first-in-human trial by Grönberg and colleagues (Wound Repair Regen 2014, PMID 25041740, n=34), in which the lowest LL-37 dose (0,5 mg/ml) achieved an approximately six-fold higher healing rate constant than placebo; the dose-response was non-monotonic, however, since the highest dose (3,2 mg/ml) showed no advantage over placebo. A 2023 RCT in Archives of Dermatological Research extended this evidence to diabetic foot ulcers and again reported enhanced healing versus placebo.

In vitro, LL-37 is active against MRSA, VRE, and representatives of the ESKAPE panel, which has made it a reference molecule for antimicrobial peptide development. Keshri and colleagues (Int J Antimicrob Agents, 2025, PMID 39643165) provide a comprehensive overview of the diverse roles of LL-37, from infection defense to cancer immunity, and a 2025 IJMS review (26(16):8103) discusses LL-37 derivatives with improved therapeutic index.

Mechanisms of Action

Membrane Disruption Plus Immunomodulation

LL-37 acts through at least two distinct modes. At higher concentrations, the cationic amphipathic helix directly permeabilizes bacterial membranes ("carpet" or toroidal-pore model). At sub-lethal concentrations, it functions as an immunomodulator: in preclinical models, it activates the proposed STING signaling pathway, recruits neutrophils, influences dendritic cell responses, and modulates epithelial cell migration in the wound context. Its transcription is closely coupled to Vitamin D status, which is why serum 25(OH)D status can be considered a relevant covariate in cathelicidin studies.

Zhao 2023 (J Med Virol, DOI 10.1002/jmv.29035) added a viral dimension. Importantly, the intervention was not synthetic oral LL-37, but an oral, LL-37-expressing recombinant Lactococcus lactis (a genetically engineered probiotic). In a randomized, open-label trial in 238 patients during the Omicron BA.5.1.3 wave, this intervention shortened the time to viral load negativity. The proposed mechanisms (STING activation, interference with spike/ACE2 binding) are hypotheses. A 2025 study additionally described that LL-37 blocks TMPRSS2-mediated cleavage of the spike protein of earlier SARS-CoV-2 variants, but not of the Omicron variants.

The 2025 sepsis and ALI literature has added another layer: Gao and colleagues (Toxins 2025;17(6):306, PMID 40559884) describe a ZBP1-autophagy axis through which LL-37 mitigates lung injury in animal models of sepsis. These findings are still preclinical, but mechanistically novel.

Quality Criteria

LL-37 is a long peptide (37 residues), and synthesis artifacts are a real concern. Researchers should insist on published analytical data rather than relying on a blanket assurance.

Purity Testing

Research-grade LL-37 should show high HPLC purity; the purity value for each batch is listed on the Certificate of Analysis (see the CoA page). A complete Certificate of Analysis includes an HPLC chromatogram, mass spectrometry confirming the expected molecular mass (approximately 4493 Da for the free acid form), counterion-corrected peptide content, and residual solvent data. For every LL-37 batch at PeptidesDirect, a Janoshik lab report is available (submitted by the manufacturer).

Storage Notes

LL-37 is more labile than small peptides like GHK-Cu or BPC-157. The lyophilized powder should be stored at -20 °C, ideally at -80 °C for long-term archiving. After reconstitution, LL-37 is light-sensitive. Use amber or foil-wrapped vials and store refrigerated (2-8 °C); a fixed shelf life cannot be guaranteed without a batch-specific stability study. Repeated freeze-thaw cycles should be avoided, so aliquoting is advisable.

EU shipping: For researchers in Europe, PeptidesDirect ships LL-37 from within the EU. Deliveries within the EU customs territory incur no customs duties or import fees, and shorter transit times can reduce the stress on a temperature-sensitive peptide. Delivery includes tracking, typically taking one to two working days within Germany and up to four working days elsewhere in the EU.

Reconstituting LL-37

The long sequence makes careful reconstitution more important than with shorter peptides. For general background, see our Peptide Storage Guide.

Choose a Batch-Specific Validated Solvent

In laboratory practice, bacteriostatic water (0,9% benzyl alcohol) is often used. This does not establish validated compatibility or stability with LL-37; the protocol should specify a suitable, batch-specific validated solvent.

Add the Solvent Slowly Along the Vial Wall

Do not inject directly onto the lyophilisate. Let the solvent run slowly down the inner wall of the vial to minimize mechanical stress on the peptide.

Swirl Gently and Protect From Light

Do not shake. Gentle swirling until the solution is clear is sufficient. After reconstitution, wrap the vial in foil or use amber glass, and refrigerate immediately.

Bacteriostatic Wateraccessories

USP-grade sterile water with 0.9% benzyl alcohol (near-neutral, ~pH 6) - the standard solvent for reconstituting lyophilized peptides. Essential accessory for any peptide research. Each vial is sealed and ready to use.

Key Evidence (2014-2026)

Four papers are worth highlighting for orientation in the current LL-37 landscape.

Grönberg 2014 (Wound Repair Regen, PMID 25041740) is a key controlled human data point. This randomized first-in-human trial (n=34) showed an approximately six-fold higher healing rate constant versus placebo at the lowest dose (0,5 mg/ml); the dose-response was non-monotonic (the highest dose, 3,2 mg/ml, showed no benefit).

Diabetic foot ulcer RCT 2023 (Arch Dermatol Res, PMID 37480520) replicated the wound-healing signal in a different chronic-wound population. The double-blind, placebo-controlled design places this trial methodologically above most of the peptide literature.

Zhao 2023 (J Med Virol, DOI 10.1002/jmv.29035) was a randomized, placebo-controlled, open-label trial in 238 hospitalized patients. The intervention was an oral, LL-37-expressing recombinant Lactococcus lactis (a genetically engineered probiotic), not the synthetic LL-37 peptide sold here. When treatment began within 6 days, the time to viral load negativity was shortened (approximately 9,8 versus 14,0 days); the proposed mechanisms (STING activation, interference with S-protein/ACE2) are mechanistic hypotheses.

Keshri 2025 (Int J Antimicrob Agents, PMID 39643165) is a current, comprehensive review of the diverse roles of LL-37 (from infection defense to cancer immunity) and a good starting point for framing the antimicrobial evidence.

On the cautious side: the dual role of LL-37 in cancer biology (Zhang et al., PMC11000334) is worth noting. LL-37 is pro-angiogenic and can be tumor-promoting in some contexts, while being tumor-suppressive in others. This duality means that extrapolating from a wound-healing or antimicrobial context to oncological settings is not straightforward.

Ordering LL-37

For a long and moderately labile peptide like LL-37, three things matter most when choosing a supplier: a batch-specific HPLC purity report (with us, a Janoshik lab report submitted by the manufacturer, viewable on the CoA page), documented cold-chain handling, and EU shipping to minimize transit times.